1. Field of the Invention
This invention relates to a magnetoresistance-effect sensor, a method of fabrication of said sensor and the application of this latter to a magnetic-domain detector. A detector of this type can be employed for reading magnetic data carriers and permits simultaneous reading of a set of data.
2. Description of the Prior Art
Sensors which utilize the linear magnetoresistance (LMR) effect are already known.
Consider a thin film of semiconductor (a few microns in thickness) in which a high current is flowing. When they are subjected to a magnetic field perpendicular to the current in the plane of the film layer, the carriers (electrons and holes) are deflected perpendicularly to the layer and in the same direction. The conventional Hall effect postulates that the currents of the two carriers are different. The forces applied to the majority carriers are cancelled by the Hall effect. In the LMR effect, the currents are balanced and no field counteracts the deflection of the carriers which collect on one of the boundary surfaces of the layer. The rates of recombination on each of these surfaces are chosen so as to be very different, thereby increasing or reducing the mean concentration of carriers in the layer according to the direction of the magnetic field. The resistance of the layer to the injected current varies linearly with the magnetic field.
At the present time, this effect is too small to permit reading of data recorded on magnetic data carriers such as a magnetic tape in which the magnetic fields developed by the written bits are too weak. In point of fact, a leakage field of a few tens of Gauss at a distance of 3 .mu.m to 5 .mu.m is not strong enough to induce a sufficiently large current in the semiconductor layer. A field having a value of several hundred Gauss is required.
It is for the reason just given that the present invention provides a sensor for amplifying and reading magnetic data and therefore magnetic fields of low intensity such as data recorded on magnetic tapes or in magnetic bubble memories.